The present invention is related to a hook needle type knitting machine improved in order to raise remarkably its work speed.
Hook needle type knitting machines are textile machines comprising a bed of hook needles performing a reciprocating movement, so that the hook needles also perform an axial reciprocating movement. Each hook needle is fed by a respective warp thread that is moved substantially axially relative to the hook needle and guided by a corresponding thread guide.
All thread guides are disposed in parallel and are carried by a traverse having substantially a rotational movement, such as to induce each thread guide to lay, above the respective advanced hook needle, the respective warp thread. The hook needles slide in respective seats, the ends of which form the shoulder for the discharge of the loops formed by the assigned hook needles.
In to such an arrangement the hook needles execute parallel loop chains and, at each loop, such chains are linked, by a weft that is laid on the warp threads before the hook needles execute their loop chain forming movement, so as to link the same weft in the successively executed loops.
Machines of this kind allow to lay, not only a weft thread, but also rubber threads and additional wefts to effect various types of fabrics with or without design.
The laid wefts and threads are guided by weft guides and thread guides carried by bars parallel to the bed of the hook needles. The bars have necessarily a limited stroke and, therefore these machines are employed mainly to knit simultaneously juxtaposed ribbon-type fabrics having the width of a few centimeters, the number of the ribbons produced depending from the width of the bed and the width of the single ribbons being processed.
The most serious disadvantage of these machines is a considerably reduced speed relative to the other types of textile machines used for the production of ribbon fabrics, and an increase of speed thereof, such as to render them competitive with other machines, is very appreciated in the art, above all because the hook needle type knitting machines are simpler and less expensive machines.
The main reasons of the speed limitation of these machines can be found in the form of the bars carrying the weft guides or the thread guides and in the kinematic connections that move respectively the bed of the hook needles and the guide said plate of said bars, in their raising and lowering movement and in the mechanism moving the same bars.
The bars, in fact, have a flattened rectangular section and therefore a limited inertia moment, and can be easily inflected due to sudden inversions of speed, so that above a certain speed they are caused to vibrate in such a way that the thread guides and the warp guides, are carried out of register, rendering practically impossible the operation of the machine.
The vertical movement of the side plates, anyway, is realized by a cam mechanism. This results in a considerable friction and it is necessary to maintain the rotation speed within enough certain limits to avoid the quick wear and the vibrations.
In a similar way the movement of the bed is effected by cams, with the same above cited inconveniences.
Another reason of the speed limitation of the hook needle type knitting machines is given by the mechanism for the axial reciprocated displacement of the bars. Such prior art mechanism includes a cam acting on a pin coaxial to the respective bar and placed in contact with the latter through a coaxial screw screwing into the bar and the flat head of which was in contact with the flat end of said pin. The contact, between the flat surfaces was subject of transversal slidings which caused fast wear of the flat faces in contact and then the need of frequent replacements.